Method of manufacture of projection-screens.



A. O. BUECHNER. METHOD OP MANUFACTURE OP PROJECTION SCREENS.

APPLICATION FILED AUG.11. 1911.

1,044,1 35, l Patented Nov. 12, 1912.

Ff?, A

f f l a WITNESSES: O INVENTOR M ATTORNEYS 'UNITED sTATEs PATENT OFFICE.

ALBERT osWALn BUECHNEB, oF ZRICH, SWITZERLAND, AssreNon To THE FIRM ory rma GESELLSCHAFT EUR TAGESLICHT-PMJEKTION. MIT BESCHBNKTER HAF- mUNG, 0F HAMBURG, GEBfMANY.

METHOD or MANUFAQTURE or PROJECTION-SCREENS.

Specification of Letters Patent. Appneaaon and August 11, 1911.

Patented Nov. 12,` 1912.

Serial No. 643,608.

'resident of Zrich, Switzerland, have invented certain new and useful Im rovements in Methods of Manufacture of rojection- Screens and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to -make and use the same. I

This invention relates to a method of manufacture of refracting or dioptric projection screens with the object inview to rovide a practical and economical procedure 1n the .prepa-ration of such screens i'n order that-the desired viewing angle may be attained.

The invention consists in producing upon a pane of suitable material, a preliminary non-plane surface'such as may be readil produced by mechanical means, and secon to alter the refiecting and refracting characteristics of the surface so formed by subsequent treatment to obtain a screen having characteristics not readily attainable by either said means or subsequent treatment alone.

The invention may be practised by first; roughening a pane of transparent material, glass for instance, by the employment of the sand blast or equivalent."instrumentalities which produces a very irregular surface with many accidental angleso and faults whicheffect partial and total reflection of iight falling upon the plane causing it to appear Whlte and to refract light transmitted through it throughout an angle wider than that desired; and subsequently` to treat the pane so roughened by the ap llcation of a lacquer or varnish'in li uid displaces thev air in the fau ts' and partially fills the steeper depressions .hardening under the influence of surface tension With an outer surface which is made up ofv myriads -of small curved rather than plane surfaces which so alters the reflecting and refracting characteristics of the pane that the white appearance disappears and the angle of` vision is narrowed. f

In the accompanying drawing the structure so attained is illustrated in section in lFigure 1 as it would aporoximately appear surfaces of these if greatly magnified, the reference letter A indicating a sand blasted glass plate and B indicating the film of lacquer or varnish applied to its roughened surface.

A modification of the manner in which this invention may. be practised involves the first step of sand blasting or otherwise producing the preliminary surface upon the pane as before and then subjecting the surface so roughened to the action of an etching agent such as for instance, hydro-fluoric acid which destroys the faults and total reflectthe projecting portions thereby producing a surface of myriads of small curved rather than plane surfaces. The structure so attained is illustrated in Fig. 3 as it would approximately appear if greatly magnified, the dotted lineC representing the profile of the glass plate A before the acid treat-ment.

Another modification of the procedure in carrying out this invention again involves the first step of sand blasting a suitable pane A, (see Fig. 2), and then entirely filling out the inequalities of the surface so produced with a transparent material D (Fig. '2) of different refractive index from that of the pane.

Still another modification of this method is to rovide by mechanical means, such as by ro ling or pressing relatively steep co-nfigurations E in the surface of a suitable QA (see Fig. 4) and then subject the configurations to an etching agent such as hydro-fiuorie acid if a glass pane be employed, to produce small irregularities upon the surfaces of these configurations E or produce upon them anyv of the alterations brought about by the second stages of the process above mentioned..

It is obvious that replicas produced from panes manufactured by `this process, though of different material are eomprehended Within the scope of this invention.

A pane prepared in accordance with this invention may be used with a rear, smooth surface silvered to afford a mirror and when so used is nevertheless a refracting screen depending for its operation upon the passage of the light through the glass to be twice refracted by the prepared surface.

What I claim is :-w

The method of manufacturing refractpane ing plane angles and rounds off the edges of e ing projection screens, consisting in produc- In testimony whereof I aiiX my signature, ing a, preliminary non-plane surface upon in presence o two Witnesses. a pane of suitable material and altering the refracting and reflecting characteristics of the surface so provided by subsequent treat- Witnesses: ment, to lessen reflection and obtain a suit- CHARLES HARRY ROECKNER, able angle of refraction. ERNEST H. L. MUMmNHoFF.

ALBERT OSWALD BUEGHNER. 

